Electro-optic device, electronic instrument, and projection display

ABSTRACT

The invention provides, an electro-optic device that can include a pair of substrates sandwiching an electro-optic substance therebetween. The electro-optic device can further include a coating member including an antistatic material and being disposed on a surface not opposing the electro-optic substance of at least one of the pair of substrates. Accordingly, problems of dust adhesion on the surface of the electro-optic device and dust projection can be solved so as to enable images with high quality to be displayed.

This is a Continuation of application Ser. No. 10/367,732 filed Feb. 19,2003. The disclosure of the prior application is hereby incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a technical field of an electro-opticdevice and an electronic instrument. More particularly the presentinvention relates to the technical field of the electro-optic device anda projection display preferably incorporated in a light valve of theprojection display that is an example of the electronic instrument.

2. Description of Related Art

Currently, an electro-optic device, such as a liquid crystal displaycapable of active matrix driving is known, which can include pixelelectrodes arrayed in a matrix arrangement, thin film transistors(referred to below as TFTs) connected to each of the electrodes, andscanning lines and data lines, which are connected each of the TFTs andrespectively arranged in parallel with line and row directions. Such anelectro-optic device has been widely used as a light valve of aprojection display, for example. The projection display can include anoptical system for guiding light emitted from a light source to thelight valve and another optical system for guiding the light transmittedthrough the light valve to a screen. At this time, controlling the lighttransmittance for each pixel enables images to be displayed on thescreen. Despite the fact that the projection display is rather compact,the images can be enlarged by the latter optical system, therebyenabling an image in comparatively large size to be displayed.

Furthermore, a projection display of such type capable of colordisplaying is known, where three of the light valves, i.e., theelectro-optic devices are prepared and three colors such as red, blue,and green are respectively projected to the three electro-optic devicesso as to be combined by an appropriate prism to form a color image.

SUMMARY OF THE INVENTION

However, the following problems have been encountered in a conventionalelectro-optic device, especially in a projection display using theelectro-optic device as a light valve. That is, in the projectiondisplay mentioned above, when dust or grime (referred to below as dustsimply) adheres on the surface of the light valve, the dust image isalso projected on the screen, which reduces image quality.

Then, in order to solve such a problem, a dust-proof glass with apredetermined thickness has been conventionally bonded on the surface ofthe light valve. Therefore, dust adheres on the dust-proof glass so asto prevent the dust from being projected on images. This is becauselight emitted from a light source is generally condensed and focused ata predetermined position within the light valve (a liquid crystal layer,for example) and then it is enlarged, and thereby the dust adhering onthe dust-proof glass with a predetermined thickness exists at a positionout of the focus (i.e., being defocused), so that the dust cannot beprojected on the screen.

However, as described above, in using such a dust-proof glass it isrequired to have “the predetermined thickness” for the dust-proof glass.This is because if the dust-proof glass has a thickness smaller thanthis predetermined thickness, the sufficient defocus effect mentionedabove cannot be obtained. The value of “the predetermined thickness”here is generally comparatively large, such as 2 mm, for example, orseveral millimeters case by case.

Taking into account that miniaturization and high fineness are generallydemanded for the projection display or the electro-optic device, theabove measure can be counter productive. For example, in a liquidcrystal display as an example of the electro-optic device, the distancebetween two substrates opposing each other and sandwiching a liquidcrystal layer therebetween, which is called a cell gap, has a gap around3 to 5 μm, or less. In this state, adding the dust-proof glass havingthe above-predetermined thickness, which surpasses the above values byfar, does not result in miniaturization and high fineness.

When the “thick” dust-proof glass mentioned above is provided, it alsobecomes problem that the heat produced by the electro-optic device isdifficult to be dissipated outside. This is because if heat more thanallowable is accumulated within the electro-optic device, the entiredevice cannot operate in a stable state. Such a problem is concernedespecially when the electro-optic device is used as the light valve ofthe projection display. This is because a comparatively high power lightsource is generally used in the projection display, so that more heattends to accumulate within the electro-optic device.

In view of such problems, it is understood that solving the dustprojection problem only by the dust-proof glass is not a preferablesolution.

The present invention has been made in view of the problems describedabove, and it is an object thereof to provide an electro-optic deviceand an electronic instrument having the electro-optic device, in whichby solving a dust projection problem, high-quality images can bedisplayed. Additionally, miniaturization of the devices can be achievedand the stable operation thereof can be performed without heataccumulated therewithin. It is another object of the present inventionto provide a projection display as an example of the electronicinstrument.

In order to solve the problems described above, an electro-optic deviceaccording to the present invention can include a pair of substratessandwiching an electro-optic substance therebetween, a display electrodedisposed above one of the pair of substrates, and wiring electricallyconnected to the display electrode directly or via a switching element.The device can also include a coating member having an antistaticmaterial and that is disposed on the surface not opposing theelectro-optic substance of at least one of the pair of substrates.

According to the electro-optic device of the present invention, byapplying an appropriate voltage to the display electrode formed on thepair of substrates via the wiring, an electric field can be applied tothe electro-optic substance so as to change the state thereof. At thistime, by projecting light transmitting from the surface not opposing theelectro-optic substance of at least one of the pair of substrates towardthat of the other of the pair of substrates, an image can be displayed.This is because the transmittance can be changed according to the changeof state of the electro-optic substance, enabling gradation display tobe performed corresponding to the change.

According to the present invention, the coating member can include anantistatic material that is provided on the surface not opposing theelectro-optic substance of at least one of the pair of substrates.Thereby, the dust projection problem described above can be effectivelysolved.

The dust adhesion frequently encountered in the past results from thatdust usually builds up static electricity. That is, if the material tobe stuck has a high electric resistance, the adhesion is extremelyliable to occur by an electrostatic force exerted between the materialand dust. Whereas according to the present invention, as describedabove, there is provided a coating member comprising an antistaticmaterial, so that dust with static electricity produced therein can beprevented from adhering thereon in advance.

Therefore, the electro-optic device according to the present inventionmakes it possible to prevent dust image from being projected in advance,enabling high quality images to be displayed. Moreover, this is becausethe dust adhesion to the electro-optic device itself is prevented inadvance. It is quite different from a conventional concept (defocusing,for example).

Accordingly, according to the present invention, a conventionally useddust-proof glass is not necessarily required, so that cost can bereduced correspondingly and the miniaturizing of the electro-opticdevice can be achieved. Also, the heat accumulated within theelectro-optic device may be easily dissipated outside. These advantagesof the present invention are highly important because the conventionaldust-proof glass generally has a large thickness as described above.

Additionally, the coating member including an antistatic material caninclude a conformation in which the surface of the coating member iscoated with powder including the antistatic material, in addition to thecase where the entire coating member consists of the antistaticmaterial.

According to the present invention, the display electrode can be thepixel electrode arrayed in a matrix arrangement formed on one of thepair of substrates while being the opposing electrode (common electrode)formed on the entire surface of the other of the pair of substrates.Also, the switching electrode can be the TFT or thin film diode (TFD).By these elements, the active matrix driving can be performed.

Furthermore, another example of the display electrode can also beassumed to be striped electrodes formed on the respective pair ofsubstrates and intersecting each other. By these elements, the passivematrix driving can be performed.

In one mode of the electro-optic device according to the presentinvention, the coating member may be provided on the other of the pairof substrates. According to this mode, in the electro-optic devicecapable of active-matrix driving, the coating member is formed on theopposing substrate, so that it is typically arranged on the plane ofincidence. Therefore, according to this mode, the dust adhesion on theplane of incidence can be prevented. Especially in this mode, thecoating member may be preferably provided on a dust-proof glass formedon the other of the pair of substrates.

By such a configuration, there is provided a conventional dust-proofglass in addition to the coating member according to the presentinvention. Therefore, according to the mode, while the dust-adhesionpreventing effect is counted on the coating member, even when dustadheres thereto, the device can also benefit from the effects ofdefocusing described above, so that the dust-projection problem is moredifficult to be produced, enabling more high-quality images to bedisplayed.

The dust-proof glass according to the mode, may be the same in thematerial and structure as a conventional one, however, the thickness canbe reduced smaller than the conventional one. This is because there isprovided the coating member according to the mode. Therefore, also inthis mode, the reduction in manufacturing cost and size of theelectro-optic device and the dissipation of heat within theelectro-optic device can be achieved correspondingly.

From such situations, according to the mode, the trade-off relationshipmay be found between the dust-projection preventing effect and theeffect of miniaturizing and heat-dissipation of the electro-opticdevice. That is, if the thickness of the dust-proof glass is increased,the former effect is more secured and the latter is reduced, and viceversa if the thickness is reduced. The thickness of the dust-proof glassaccording to the mode is determined in view of such situations. Morespecifically, the thickness may be appropriately determined principally,experientially, experimentally, or with simulation.

According to another mode of the electro-optic device, the coatingmember may constitute at least part of an anti-reflection coat.According to this mode, the coating member constitutes at least part ofthe anti-reflection coat generally bonded on the external surface of theelectro-optic substance as a constituent element, so that the entiredevice can be simplified and made more efficient.

The anti-reflection coat is a member disposed on an interface, acrosswhich the refractive index changes, such as the interface between airand a glass substrate, and it is an optical element for efficientlyguiding light from air to the glass substrate or vice versa, forexample, with producing light reflection on the interface as small aspossible. According to the mode, the anti-reflection coat may adopt anyof various generally known configurations.

The coating member may constitute at least part of the anti-reflectioncoat according to the mode, so that under certain circumstances, thecase, where the entire anti-reflection coat is a coating member, i.e.,the entire anti-reflection coat serves as the coating member, may beadapted to the device.

More specifically in the mode, cases are assumed where theanti-reflection coat is constituted of a conductive material and theanti-reflection coat is constituted of an antistatic material. Accordingto this mode, the anti-reflection coat may preferably have amulti-layered structure in particular. In such a structure, themulti-layered structure may be provided with one arbitrary layer of thecoating member or not less than two layers thereof.

As a more specific mode, there may be adopted a four-layer structure ofZrO₂, the coating member including ITO, SiO₂, and ZrO₂ arranged in thatorder from the light incident side. Generally, if the top layer is alight-incident plane, the next top layer may preferably include thecoating member according to the present invention (the above-mentionedspecific mode is an example thereof). Because in this case, the originalfunction of the anti-reflection coat has an accommodating harmoniousbalance with the function to be exerted by the coating member.

In another mode of the electro-optic device according to the presentinvention, the coating member including a transparent conductivematerial. According to this mode, since the coating member is atransparent material, there may be provided a coating member capable ofpreventing dust adhesion without damaging the transparency orpermeability of the entire electro-optic device as a whole.

As for the transparent conductive material according to the mode, theremay specifically be ITO (indium tin oxide) or IZO (indium zinc oxide).In this mode, in particular, the coating member including thetransparent conductive material may be preferably grounded. Because insuch a structure, the dust adhesion preventing operation can be moresecurely demonstrated. If the coating member is at floating potential,this may inversely affect the operation of the electro-optic device suchthat useless capacity coupling may be possibly produced, whereas,according to the mode, there is no such possibility.

In another mode of the electro-optic device according to the presentinvention, a separation optical element may be further providedseparately from the electro-optic device, and the coating member isprovided in the separation optical element. According to this mode, anoptical element, which is usually arranged outside the electro-opticdevice, such as a polarizing plate or a phase contrast plate, isprovided separately from the electro-optic device, while the coatingmember is provided in the separation optical element. Thereby, thefollowing advantages are shown.

In other words, since the polarizing plate or the phase contrast plateis also one of optical elements transmitting light contributed to imageformation, if dust adheres on the surface of the optical element, thedust projection problem cannot be effectively solved. Whereas, accordingto the mode, since the coating member can also be bonded on thepolarizing plate or the phase contrast plate, the surface of thepolarizing plate or the phase contrast plate is also prevented frombeing stuck by dust, resulting in efficiently solving the problem ofdust projection on images.

Such an advantage is effective especially in the case where parallellight is projected to the optical element according to the mode. Becauseeven when the optical element is separated, a defocusing effect for theparallel light is not sufficiently demonstrated.

According to the mode, even when the coating member is providedseparately from the electro-optic device, there can be no problem if inaddition to the above coating member, another coating member is providedand directly bonded on at least one of the pair of the substratesconstituting the electro-optic device. That is, for example, there maybe both of coating members bonded on both surfaces of the electro-opticdevice and coating members bonded on both surfaces of the polarizingplate or the phase contrast plate mentioned above (in this case, fourcoating members existing in total). Under certain circumstances, thecoating member may be obviously provided only on the separately arrangedoptical element.

As described above, in the structure where the polarizing plate or thephase contrast plate is provided separately from the electro-opticdevice, the following advantages based on the structure itself can beobtained. That is, if the optical element such as the polarizing plateor the phase contrast plate is directly bonded on at least one of thepair of the substrates constituting the electro-optic device, when acomparatively large pin hole exists in the optical element, a pin-holeprojection problem arises in the same way as the dust projectionproblem. However, in this mode, there is scarcely such apprehension.Because the polarizing plate or the phase contrast plate is providedseparately from the electro-optic device, so that the defocusing effectmay be expected accordingly. This fact is applicable to the case where aplurality of the optical elements are provided and they are bondedtogether with an appropriate adhesive. Because if the adhesive includesdust, the projection problem of the dust in the adhesive may arise inthe same way as described above.

Finally, according to this mode, the design rule about the opticalelement such as the polarizing plate or the phase contrast plate can bealleviated. That is, even when a comparatively large pin hole exists inthe optical element, or dust comes to stay in between a plurality ofoptical elements (between the polarizing plate and the phase contrastplate, for example), they cannot be projected on images by virtue of thedefocusing effect. Accordingly, according to the mode, a totallyinexpensive electro-optic device can be provided.

In another mode of the electro-optic device according to the presentinvention, an electrical resistance of the coating member is 10¹²Ω orless. According to this mode, the electrical resistance of the coatingmember may be pertaining to any one of an antistatic region, aconductive region, and a conductor region, so that the dust-adhesionpreventing effect described above can be more securely expected.

In order to solve the problems described above, an electro-optic deviceaccording to the present invention can include a pair of substratessandwiching an electro-optic substance therebetween, a display electrodedisposed on one of the pair of substrates, wiring connected to thedisplay electrode directly or via a switching element, and a coatingmember disposed on a surface not opposing the electro-optic substance ofat least one of the pair of substrates, the coating member including asurface-active agent at least on the surface.

According to the electro-optic device of the present invention, in thesame way as the electro-optic device described above, through electricfield application on an electro-optic substance and changes of state ofthe electro-optic substance caused by the electric field application,images can be displayed.

According to the present invention, the coating member is provided on asurface not opposing the electro-optic substance of at least one of thepair of substrates, and the coating member includes a surface-activeagent at least on the surface. A surface-active agent can be classifiedbroadly into an anionic type and a cationic type, any one of these maybe used according to the present invention. At all events, by thebehavior of the surface-active agent, dust adhesion can be prevented inadvance according to the present invention. Because this is just such asituation that the dust adhesion may be mainly caused by anelectrostatic force as described above. Therefore, also in theelectro-optic device according to the present invention, the dustprojection can be prevented in advance, enabling high-quality images tobe displayed.

In order to solve the problems described above, an electronic instrumentaccording to the present invention can include the above-describedelectro-optic device according to the present invention (includingvarious modes described above). Since the electronic instrumentaccording to the present invention can include the above-describedelectro-optic device according to the present invention, variouselectronic instruments capable of displaying high-quality imagessubstantially without dust-projection problem can be achieved, such as aliquid crystal TV, mobile phone, electronic pocket book, word processor,viewfinder or direct-view monitor video tape recorder, workstation,phonovision, POS terminal, touch panel, and the like.

In order to solve the problems described above, a projection displayaccording to the present invention can include a light valve having theabove-described electro-optic device according to the present invention(including various modes described above), a light source for sendingprojection light to the light valve, an optical system for projectingthe projection light emitted from the light valve, and a blower forblowing air to the light valve.

According to the projection display of the present invention, the lightemitted from the light source is projected to the electro-optic deviceas the light valve, and then enlarged by the optical system after beingemitted from the electro-optic device, enabling a comparatively largeimages to be projected on a screen. Also, according to the presentinvention, the blower for blowing air to the light valve is provided,which enables the light valve to be cooled.

In the present invention, the blower can provide the followingadvantages. In the projection display of the present invention, sincethe light valve includes the above-described electro-optic deviceaccording to the present invention, heat dissipation from the lightvalve is facilitated by eliminating the dust-proof glass or reducing thethickness thereof, as already described. Therefore, the blower accordingto the present invention is not required to have large power, becausewith not large power, sufficient cooling can be performed. Therefore,according to the present invention, the power consumption required forthe blower can be reduced, and so-called hissing sound generated by theblower can be reduced because the power may be reduced, enabling a quietprojection display to be provided.

Also, according to the blower of the present invention, the dust comingclose to adhere on the surface of the light valve can be blown off justbefore adhesion. Since the light valve of the present inventionparticularly includes the above-described electro-optic device accordingto the present invention, dust adhesion can be prevented by its own in aconsiderable high degree of certainty. This advantage can be moreenhanced by adding the blower. Therefore, according to the projectiondisplay of the present invention, images with higher quality can bedisplayed.

Such operations and other advantages of the present invention willbecome apparent as the following description of embodiments proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numerals reference like elements, and wherein:

FIG. 1 is a plan view of a TFT array substrate in an electro-opticdevice according to an exemplary embodiment of the present inventionviewed with various elements mounted thereon from an opposing substrate;

FIG. 2 is a sectional view at the line H-H′ of FIG. 1;

FIG. 3 is an enlarged view of a first embodiment of the presentinvention showing the inside the circle indicated by symbol CR in FIG.2;

FIG. 4 is a drawing of a second embodiment of the present invention,which is similar to FIG. 3 and different from FIG. 3 in the point that adust-proof glass is provided;

FIG. 5 is a drawing of a third embodiment of the present invention,which is similar to FIG. 3 and different from FIG. 3 in a structure ofan AR coat;

FIG. 6 is a drawing of a fourth embodiment of the present invention,which is similar to FIG. 3 and different from FIG. 3 in the point that acoating member constitutes part of a separation optical element;

FIG. 7 is a diagrammatic sectional view of a color liquid crystalprojector as an example of the projection display;

FIG. 8 is an equivalent circuit diagram of various elements and wiringarranged in a plurality of pixels arrayed in a matrix arrangement andconstituting an image display region of an electro-optic deviceaccording to the embodiment of the present invention;

FIG. 9 is a plan view of a plurality of pixel-groups adjacent to eachother on a TFT array substrate, on which data lines, scanning lines, andpixel electrodes are mounted; and

FIG. 10 is a sectional view at the line A-A′ of FIG. 9.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Exemplary embodiments according to the present invention will bedescribed below with reference to the drawings. In the embodimentsbelow, an electro-optic device according to the present invention isincorporated in a liquid crystal apparatus.

First, the entire structure of an electro-optic device according to afirst embodiment will be described with reference to FIGS. 1 to 3. FIG.1 is a plan view of a TFT array substrate having various elementsmounted thereon and viewed from an opposing substrate 20; FIG. 2 is asectional view at the line H-H′ of FIG. 1; and FIG. 3 is an enlargedview of inside the circle indicated by symbol CR in FIG. 2. In addition,in order that layers and members have recognizable sizes in FIG. 3, theyare displayed thereon with respectively different contraction scales.

Referring to FIGS. 1 and 2, the electro-optic device according to thefirst embodiment can include a TFT array substrate 10 and the opposingsubstrate 20, which are arranged to oppose each other. Between the TFTarray substrate 10 and the opposing substrate 20, a liquid crystal 50 isenclosed, and the TFT array substrate 10 and the opposing substrate 20are bonded together with a sealing material 52 provided on a sealingregion located in the periphery of an image display region 10 a. Theliquid crystal 50 can be supplied by blending one kind or several kindsof nematic liquid crystal so as to have a predetermined oriented statebetween a pair of oriented films, which will be described in greaterdetail below.

The image display region 10 a is defined by a region having pixelelectrodes 9 a arrayed in a matrix arrangement, TFTs connected to eachof the pixel electrodes 9 a, scanning lines and data lines connected tothe TFTs (each of them will be described below with reference to FIGS. 8to 10) formed on the TFT array substrate 10, or the image display region10 a is also defined by a region opposing the above region and having anopposing electrode 21 formed on the opposing substrate 20, the regionbeing defined by a square framed light-shielding film 53 shown in FIG.1.

Through the image display region 10 a, light can transmit from this sideof the plane of FIG. 1 toward the other side when facing the plane(i.e., from the opposing substrate 20 toward the TFT array substrate10), resulting in contributing to image display. This is because thepixel electrode 9 a, part of the pixel electrode 9 a, or the opposingelectrode 21 is made of a transparent material while the state of theliquid crystal 50 is changed by applying an electric field to each ofthe pixel electrodes 9 a. Also, one pixel is defined by one unitincluding at least any one of one pixel electrode 9 a and one TFT.

The sealing material 52, as shown in FIG. 1, is provided so as tosurround the image display region 10 a. However, in order to bringliquid crystal within the clearance sandwiched between the TFT arraysubstrate 10 and the opposing substrate 20, as shown in the lowerportion of FIG. 1, a cut-out is formed in part of the sealing material52 as a liquid crystal filling port 52 a. In the completed electro-opticdevice, in order to prevent the liquid crystal 50 brought into theclearance from leaking outside, a sealing material 54 made of aUV-curable thermosetting acrylic resin is used in a portioncorresponding to the liquid crystal filling port 52 a.

The sealing material 52 may be made of a UV-curable resin or athermosetting resin, for example. In order to bond the TFT arraysubstrate 10 and the opposing substrate 20 together, both the substrates10 and 20 are pushed by an appropriate pressure applied thereto, and thesealing material is irradiated with a UV ray if the sealing material isthe UV-curable resin, or it is heated if it is the thermosetting resin,so as to be cured.

Also, the sealing material 52 contains gap materials (not shown)dispersed therein as a kind of spacer so as to have a predetermined cellgap, which is the gap space between both the substrates 10 and 20. Thegap material is generally made of glass fiber or glass beads having asubstantially spherical shape.

Referring to FIG. 2, on the TFT array substrate 10, there are providedan oriented film 16 formed over the pixel electrode 9 a having the TFTsfor switching pixels and wiring such as scanning lines and data linesalready formed therein. On the other hand, on the opposing substrate 20,there can be provided an upper light-shielding film 23 arrayed in alattice that defines an aperture region substantially corresponding to aregion having the pixel electrode 9 a formed thereon, the opposingelectrode 21 made of a transparent material, such as ITO, and formed onthe upper light-shielding film 23, and an oriented film 22 furtherformed on the opposing electrode 21 by a coating process, sinteringprocess, and rubbing treatment.

According to the first embodiment in particular, as shown in FIG. 2 andFIG. 3 which is an enlarged view of part of FIG. 2, the opposingsubstrate 20 can be provided with an AR (anti-reflection) coat 500, apolarizing plate 701, and a coating member 401 formed on the side notopposing the liquid crystal 50 (an upper portion of FIG. 3) and arrangedin that order from the opposing substrate 20. Among them, the AR coat500 is constituted of a single layer or a plurality of layers ofzirconia (ZrO₂) or silica (SiO₂). For example, the AR coat 500 may havea four-layer structure of zirconia, silica, zirconia, and silica, or itmay also have a multi-layered structure more than four layers byrepeating the zirconia and silica. Thereby, in between members havingdifferent refractive indexes, such as from an airspace (an upper portionof FIG. 3) to inside the opposing substrate 20 (a lower portion of FIG.3), loss due to useless reflection can be avoided enabling efficientlight-guide between the members to be performed. The polarizing plate701 properly polarizes light to be incident in the liquid crystal 50.Thereby, when there is a predetermined relationship between thepolarizing state and the oriented state by properly determining theoriented state of the liquid crystal 50, incident light, which ispolarized light, substantially perfectly transmits the members, fromwhich adjustment can be performed until the state that the incidentlight is substantially perfectly shielded.

The coating member 401, being characteristic in the first embodiment,made of ITO which is an example of a transparent conductive material. Atleast part of the coating member 401 is connected to electrical wiringso as to be grounded.

Other than the configuration described above, in FIGS. 1 to 3, on aregion outside the sealing member 52, there are provided a data-linedriving circuit 101 that drives the data line, which will be describedlater, by supplying an image signal to the data line at a predeterminedtiming and external-circuit connection terminals 102 formed along oneside of the TFT array substrate 10, while scanning-line driving circuits104 can be formed along two sides adjacent to the one side for drivingthe scanning line, which will be described later, by supplying an imagesignal to the scanning line at a predetermined timing. In addition, aslong as the delay of the scanning signal supplied to the scanning lineis not important, it is of course enough to have one scanning-linedriving circuit 104 on one side. Also, the data-line driving circuits101 may be arranged along sides of the image display region 10 a on bothsides.

On the one remaining side of the TFT array substrate 10, a plurality oflines of wiring 105 are arranged for connecting between thescanning-line driving circuits 104 arranged on both sides of the imagedisplay region 10 a. Also, at least at one position of corners of theopposing substrate 20, a vertically conducting material 106 is providedfor conducting electricity between the TFT array substrate 10 and theopposing substrate 20.

On the TFT array substrate 10, in addition to the data-line drivingcircuit 101 and the scanning-line driving circuit 104, there may beprovided a sampling circuit for applying an image signal to a pluralityof data lines 6 a at a predetermined timing, a pre-charge circuit forsupplying a pre-charge signal in a predetermined voltage level to aplurality of the data lines 6 a prior to the image signal, and achecking circuit for checking the quality or a defect of theelectro-optic device during manufacturing or at shipment.

The electro-optic device configured as above according to the firstembodiment has the following advantages because of the existence of thecoating member 401 described above.

First, according to the first embodiment, dust scarcely adheres on themost external surface of the electro-optic device (the highest surfaceof FIG. 3) by providing the coating member 401 having ITO which is anexample of the transparent conductive material. This is because thecoating member 401 has electrical conductivity, which prevents thecharged dust from adhering in advance by an electrostatic force.Therefore, according to the first embodiment, high-quality images can bedisplayed substantially eliminating the problem of dust projection.

According to the electro-optic device of the first embodiment, as shownin FIGS. 2 and 3, the dust-proof glass need not be provided. This isbecause it is not substantially necessary to worry about the dustadhesion any more by means of the effect of the coating member 401described above. Therefore, according to the first embodiment,conventional problems due to the dust-proof glass having a comparativelylarge thickness for achieving the dust projection problem cannot beproduced. In other words, in the first, the cost due to the dust-proofglass can be eliminated, in the second, the entire electro-optic devicecan be miniaturized, and at the third, the heat accumulated within theelectro-optical device can be easily dissipated outside so as to achievethe precise operation of the electro-optic device.

As described above, according to the first embodiment, the advantagesdescribed above can be achieved.

In addition, the coating member 401 is made of ITO in the abovedescription; alternatively, an IZO, which is another example of thetransparent conductive material, may be used. Also, the coating member401 is not necessarily to be a conductive material, and in view of theoperation to prevent charged dust from adhesion, the coating member 401may be made of at least an antistatic material. There are various suchmaterials; more specifically, when a material having an electricalresistance of 10¹²Ω or less for the coating member 401 is selected, areasonable effect of preventing the dust adhesion may be expected.

Moreover, according to the present invention, instead of the aboveconfiguration, or in addition thereto, a surface-active agent may becontained within the surface of the coating member. Even in thisconfiguration, substantially the same advantage as the aboveconfiguration can be obtained. This is because a surface-active agenthaving an antistatic effect is known (in particular an anionic system,for example) and when this is provided on the surface of the coatingmember, the effect of preventing the dust adhesion may be expected.

Also, in FIGS. 2 and 3, the coating member 401 is provided only on theopposing substrate 20, however, it should be understood the presentinvention is not limited to this configuration. Under certaincircumstances, the coating member 401 may be provided only on the TFTarray substrate 10, or on both the TFT array substrate 10 and theopposing substrate 20.

Furthermore, in FIGS. 2 and 3, there is provided the polarizing plate701, however it should be understood that it is not necessarilyprovided. That is, in such a case, the arrangement is the order of theopposing substrate 20, the AR coat 500, and the coating member 401 fromthe bottom of FIG. 3. In this case, if the polarizing plate 701 isfurther provided, it may also be separated from the body of theelectro-optic device (see a fourth embodiment which will be describedlater).

Incidentally, various modifications described above may be incorporatedas they are or in an appropriately modified state into severalembodiments, which will be described later, and they are of coursewithin the scope of the present invention.

A second embodiment according to the present invention will be describedbelow with reference to FIG. 4. FIG. 4 is a drawing similar to FIG. 3showing a mode different from that of FIG. 3. The elements shown in FIG.4 and designated by like reference characters common to FIG. 3 are thesame as those of the first embodiment, so that descriptions thereof areomitted. This is the same as those of from a third embodiment onward,which will be described below.

According to the second embodiment, it differs from the first embodimentin that a dust-proof glass 901 is provided. That is, the opposingsubstrate 20 is provided with the dust-proof glass 901, the AR coat 500,the polarizing plate 701, and the coating member 401 formed in thatorder from the opposing substrate 20. The dust-proof glass 901 may bemade of an appropriate glass material.

According to the second embodiment described above, while thedust-adhesion preventing effect is counted on the coating member 401,the device can also benefit from the effects of defocusing by thedust-proof glass 901, so that the dust-projection problem is moredifficult to be produced. That is, even when dust adheres on the toplayer on the plane of FIG. 4, since the position is off a focal point tosome extent, the dust image can be prevented in advance from beingprojected on a screen.

In addition, the thickness of the dust-proof glass 901 can be reducedsmaller than the conventional one. Specifically, the thickness of thedust-proof glass has been conventionally required to be 2 mm or more forhaving sufficient defocusing effects; whereas according to the secondembodiment, such a thickness is not necessary. Therefore, also in thesecond embodiment, the reduction in size of the electro-optic device andeasiness of the heat dissipation can be enjoyed according to thereduction in thickness.

A third embodiment according to the present invention will be describedbelow with reference to FIG. 5. FIG. 5 is a drawing similar to FIG. 3showing a mode different from that of FIG. 3.

According to the third embodiment, it differs from the first embodimentin that an AR coat 501 has characteristic features. In other words, asshown in FIG. 5, the AR coat 501 has a four-layer structure of a firstzirconia layer 502, a silica layer 503, an ITO layer 403, and a secondzirconia layer 504 arranged in that order from the bottom of the planeof the figure. Among them, the ITO layer 403 corresponds to an exampleof “the coating member” according to the present invention. That is,according to the third embodiment, the AR coat 501 itself hasconductivity. Even such a structure obviously demonstrates substantiallythe same effects as those of the first embodiment.

According to the present invention, in addition to the configuration ofthe AR coat 501 described above, it should be understood that othervarious configurations may be obviously adopted. For example, in amulti-layered structure, in which a zirconia layer and a silica layerappear alternately, one arbitrary layer or not less than two layers maybe an ITO layer which is the coating member. However, in general, thenext top layer may preferably include the coating member comprising ananti-static material according to the present invention. Thereby, theoriginal functions of AR coat 501, which are anti-reflection and dustadhesion, can be demonstrated most effectively.

A fourth embodiment according to the present invention will be describedbelow with reference to FIG. 6. FIG. 6 is a drawing similar to FIG. 3showing a mode different from that of FIG. 3.

The fourth embodiment is a modification of the third embodiment. Thatis, referring to FIG. 6, an AR coat 501A containing a coating member 404a, an AR coat 501B containing a coating member 404 b, which are as shownin FIG. 5, and a polarizing plate 701 clamped by these two AR coats 501Aand 501B (this united structure is referred to below as a separationoptical element) are arranged separately from the surface of theopposing substrate 20. By such a configuration, in the separationoptical element, while the dust-adhesion preventing effect isdemonstrated by the coating members 404 a and 404 b, even without thedust-proof glass, since the separation optical element is arrangedseparately from the electro-optic device body, a predetermineddefocusing effect can be obtained. Therefore, according to the fourthembodiment, the dust projection also is scarcely produced on images,enabling high-quality images to be displayed.

Referring to FIG. 6, in addition to the coating members 404 a and 404 bincluded in the separation optical element, a coating member 404 cexists on the opposing substrate 20 in the electro-optic device itself.This coating member 404 c, as shown in the third embodiment, alsoconstitutes part of an AR coat 501C. According to the present invention,either structure, a structure in which the coating member is arrangedseparately from the electro-optic device as mentioned here or astructure in which the coating member is bonded to the electro-opticdevice, can be taken without any problems. It would be rather morepreferable to take this structure in view of solving the dust-projectionproblem.

In the above description, the separation optical element is constitutedof the AR coats 501A and 501B and the polarizing plate 701, however, itshould be understood that the present invention is not limited to such astructure. For example, in addition to the elements shown in FIG. 6, aphase contrast plate may be arranged.

Furthermore, the modification of the third embodiment is only shown inFIG. 6; as for the second to fourth embodiments, the separatedseparation optical element may be obviously provided identically to FIG.6.

A fifth embodiment according to the present invention will be describedbelow with reference to FIG. 7. The fifth embodiment is an example inwhich the electro-optic device according to the embodiments describedabove is incorporated to a projection display as an example of anelectronic instrument. FIG. 7 is a diagrammatic sectional view of acolor liquid crystal projector as an example of the projection display.

Referring to FIG. 7, a liquid crystal projector 1100 according to thefifth embodiment as an example of the projection display comprises threeliquid crystal modules including a liquid crystal device having adriving circuit mounted on a TFT array substrate, which are prepared fora projector using light valves 100R, 100G, and 100B for R, G, and B,respectively. The electro-optic devices according to the above-describedembodiments can be used for the three light valves 100R, 100G, and 100B.

In the liquid crystal projector 1100, projection light emitted from awhite-light-source lamp unit 1102, such as a metal halide lamp isdivided into optic elements R, G, and B corresponding to the threeprimary colors R, G, and B by three mirrors 1106 and two dichroicmirrors 1108 so as to be guided to the light valves 100R, 100G, and100B, corresponding to each color, respectively. At this time, the Blight is especially guided via a relay lens system 1121 including anincidence lens 1122, a relay lens 1123, and an output lens 1124 thatprevents light loss due to a long optical path. The optic elementscorresponding to the three primary colors respectively modulated by thelight valves 100R, 100G, and 100B is combined again by a dichroic prism1112, and then it is projected on a screen 1120 via a projection lens1114 as color images.

Also, the projection color display is provided with a blower 1141mounted for sending air to the light valves 100R, 100G, and 100B. It isan object of the blower 1141 to reduce the heat accumulation in thelight valves 100R, 100G, and 100B mainly due to powerful light emittedfrom the lamp unit 1102. These elements mentioned above are totallyaccumulated within a mould 1151.

According to the fifth embodiment having such a structure, since theelectro-optic devices according to the above-described embodiments areincorporated in the light valves 100R, 100G, and 100B, the dust adhesionpreventing effect may be demonstrated in the light valves 100R, 100G,and 100B in substantially the same way as described above. Inparticular, since after the light combing by the dichroic prism 1112,zooming is performed by the projection lens 1114 according to the fifthembodiment as shown in FIG. 7, the advantage that dust adhesion is notproduced is especially significant.

Constituting the light valves 100R, 100G, and 100B of electro-opticdevices according to the above-described embodiments means that the heatdissipation without the dust-proof glass or by reducing the thicknessthereof can be efficiently performed, so that it is not required to haveespecially high power of the blower 1141 according to the fifthembodiment. Accordingly, a quiet projection color display withconsumption power smaller than in a conventional one can be provided. Bythe existing of the blower 1141, dust, which is coming close to adhereon the light valves 100R, 100G, and 100B, is blown off, so thatproviding the blower 1141 takes a preferable effect also in this aspect.

The projection display has been described above as an example of theelectronic instrument, however, it should be understood that the presentinvention is not limited to such a structure and the invention can be ofcourse applied to a liquid crystal display for mobile phones andpersonal computers as another examples of the electronic instrument.

The inside structure of the electro-optic device, such as the structureof a TFT, pixel electrode, scanning line, and data line, which are notdescribed above, and operations thereof will be collectively describedbelow.

First, a pixel section of the electro-optic device according to theembodiment of the present invention will be described with reference toFIGS. 8 to 10. FIG. 8 is an equivalent circuit diagram of variouselements and wiring in a plurality of pixels arrayed in a matrixarrangement and constituting an image display region of theelectro-optic device. FIG. 9 is a plan view of a plurality ofpixel-groups adjacent to each other on a TFT array substrate, on whichdata lines, scanning lines, and pixel electrodes are mounted; and FIG.10 is a sectional view at the line A-A′ of FIG. 9. In addition, in orderthat layers and members have recognizable sizes in FIG. 10, they aredisplayed thereon with respectively different contraction scales foreach layer and member.

Referring to FIG. 8, in a plurality of pixels arrayed in a matrixarrangement and constituting an image display region of theelectro-optic device according to the embodiment, each includes a pixelelectrode 9 a, a TFT 30 for switching control of the pixel electrode 9a, and a data line 6 a electrically connected to a source of the TFT 30,image signals being supplied to the data line. The image signals S1, S2,. . . , Sn to be written in the data line 6 a may be sequentiallysupplied in that order, or they may be supplied for each group to aplurality of the data lines 6 a adjacent to each other.

To a gate of the TFT 30, a scanning line 3 a is electrically connected,so that scanning signals G1, G2, . . . , Gm are sequentially applied tothe scanning line 3 a in that order at a predetermined pulsing timing.The pixel electrode 9 a is electrically connected to a drain of the TFT30, into which the image signals S1, S2, . . . , Sn supplied from thedata line 6 a are written at a predetermined timing by closing theswitch of the TFT 30 as a switching element for a predetermined periodof time.

The image signals S1, S2, . . . , Sn written into liquid crystal as anexample of an electro-optic substance at a predetermined level via thepixel electrode 9 a are held for a predetermined period of time inbetween an opposing electrode formed on the opposing substrate. Theorientation or order of molecular assembly of the liquid crystal ischanged by a voltage level applied thereto so as to modulate light,enabling gradation display. If being in a normally white mode, thetransmittance of incident light decreases corresponding to the voltageapplied thereto in pixel units. If being in a normally black mode, thetransmittance of incident light increases corresponding to the voltageapplied thereto in pixel units, so that the light with contrastcorresponding to an image signal is projected as a whole from theelectro-optic device.

Wherein, in order to prevent the held image signals from being leaked, astorage capacitance 70 is added in parallel to a liquid crystalcapacitance formed between the pixel electrode 9 a and the opposingelectrode. The storage capacitance 70 is arranged in parallel with thescanning line 3 a and includes a capacitance electrode on a fixedpotential side and a capacitance line 300 fixed at a constant potential.

The more practical structure of the electro-optic device, in which thecircuit operation described above is performed by the above-mentioneddata line 6 a, scanning line 3 a, and TFT 30, will be described belowwith reference to FIGS. 9 and 10. In addition, the coating member shownin FIGS. 2 to 6 is not shown in FIG. 10.

The electro-optic device according to the embodiment, as shown in FIG.10 which is a sectional view at the line A-A′ of FIG. 9, can include atransparent TFT array substrate 10 and a transparent opposing substrate20. The TFT array substrate 10 is made of a quartz substrate, glasssubstrate, or silicon substrate, for example, and the opposing substrate20 is made of a glass substrate or quartz substrate, for example.

As shown in FIG. 10, the TFT array substrate 10 is provided with thepixel electrode 9 a and the oriented film 16 formed thereon. The pixelelectrode 9 a comprises a transparent conductive film such as an ITO(indium tin oxide) film. On the other hand, the opposing substrate 20comprises the opposing electrode 21 formed along the entire surfacethereof and the oriented film 22 formed thereunder. Among them, theopposing electrode 21 also comprises a transparent conductive film suchas an ITO film as the pixel electrode 9 a.

On the other hand, referring to FIG. 9, a plurality of the pixelelectrodes 9 a are arrayed in a matrix arrangement on the TFT arraysubstrate 10 (the contour being indicated by dotted lines 9 a′), andalong lengthwise and crosswise boundaries between the pixel electrodes 9a, the data lines 6 a and the scanning lines 3 a are respectivelyarranged. The scanning line 3 a is arranged so as to oppose a channelregion 1 a′ in a semiconductor layer 1 a and shown by an upward slopingshaded region on the plane of the figure, and it serves as a gateelectrode. That is, each intersecting position between the scanning line3 a and the data line 6 a is provided with the TFT 30 for switchingpixels, in which a main line of the scanning line 3 a is arranged andopposed to the channel region 1 a′ as the gate electrode.

The TFT 30, as shown in FIG. 10, has an LDD (lightly doped drain)structure, and it can include the scanning line 3 a serving as the gateelectrode as mentioned above; the channel region 1 a′ made of apolysilicon film for example, in which a channel is formed by anelectric field from the scanning line 3 a, of the semiconductor layer 1a; an insulating film 2 including a gate insulating film for insulatingthe scanning line 3 a from the semiconductor layer 1 a; and a lightlydoped source region 1 b, lightly doped drain region 1 c, heavily dopedsource region 1 d, and heavily doped drain region 1 e, which are formedon the semiconductor layer 1 a.

The TFT 30 may preferably have the LDD structure as shown in FIG. 10, orit may also have an offset structure in which impurities are notimplanted in the lightly doped source region 1 b and the lightly dopeddrain region 1 c, or the TFT 30 may be a self-aligned TFT in whichimpurities are implanted in high concentrations using the gate electrodecomprising part of the scanning line 3 a as a mask so as to form aheavily doped source region and a heavily doped drain region in aself-aligned manner. According to the embodiment, only one gateelectrode of the TFT 30 for switching pixels is arranged between theheavily doped source region 1 d and the heavily doped drain region 1 e;alternatively, two or more gate electrodes may be arranged therebetween.Furthermore, the semiconductor layer 1 a constituting the TFT 30 may bea non-monocrystal layer or a monocrystal layer. The monocrystal layermay be structured by a known method such as a bonding method. Themonocrystal semiconductor layer 1 a may offer technical advantagesespecially to peripheral circuits.

On the other hand, referring to FIG. 10, the storage capacitance 70comprises a relay layer 71, connected to the heavily doped drain region1 e and the pixel electrode 9 a of the TFT 30, as a capacitanceelectrode on a pixel potential side; and part of the capacitance line300 as the capacitance electrode on a fixed potential side, arranged andopposed with a dielectric film 75 therebetween. The storage capacitance70 enables potential holding characteristics in the pixel electrode 9 ato be conspicuously improved.

The relay layer 71, made of a conductive film, functions as thecapacitance electrode on a pixel potential side. Alternatively, therelay layer 71 may be made of a single layer film or multi-layered filmcontaining a metal or an alloy in the same way as that of thecapacitance line 300 which will be described later. The relay layer 71,in addition to the function as the capacitance electrode on a pixelpotential side, has a function of relaying and connecting between thepixel electrode 9 a and the heavily doped drain region 1 e of the TFT 30via contact holes 83 and 85. The capacitance line 300 is made of aconductive layer including metal or metal alloy for example andfunctions as the capacitance electrode on a fixed potential side. Thecapacitance line 300 viewed planarly, as shown in FIG. 9, is formed byoverlapping on a forming region of the scanning line 3 a. Morespecifically, the capacitance line 300 includes a main line extendingalong the scanning line 3 a, projections upward projecting along thedata line 6 a in the plane of the figure from each of positionsintersecting with the data lines 6 a, and a contracted section in whicha position corresponding to the contact hole 85 contracts slightly.Among them, the projection contributes to increasing the forming regionof the storage capacitance 70 using a region above the scanning line 3and a region under the data line 6 a.

Such a capacitance line 300, preferably made of a conductivelight-shielding film containing a high-melting metal, has a function ofa light-shielding layer for shielding the TFT 30 from incident lightabove the TFT 30, in addition to the function as the capacitanceelectrode on a fixed potential side of the storage capacitance 70. Also,the capacitance line 300 may preferably extend from the image displayregion 10 a, on which the pixel electrode 9 a is arranged, to theperiphery thereof so as to be electrically connected to a constantpotential source at a fixed potential. The dielectric film 75, as shownin FIG. 10, is made of an HTO (high temperature oxide) film with acomparatively small thickness of 5 to 200 nm, a silicon oxide film suchas an LTO (low temperature oxide) film, or a silicon nitride film. InFIGS. 9 and 10, in addition to the above elements, a lowerlight-shielding film 11 a is arranged under the TFT 30. The lowerlight-shielding film 11 a is patterned in a lattice so as to define anopen region of each pixel. In addition, the open region is also definedby the data lines 6 a shown in FIG. 9 and the capacitance lines 300intersecting therewith. The lower light-shielding film 11 a, in order toavoid inversely effecting the TFT 30 by changes in potential thereof, inthe same way as in the capacitance line 300 mentioned above, may extendfrom the image display region to the periphery thereof so as to beconnected to a constant potential source.

Also, under the TFT 30, an underlying insulation film 12 is provided.The underlying insulation film 12, in addition to a function ofinterlayer-insulating the TFT 30 from the lower light-shielding film 11a, has a function of preventing characteristics of the TFT 30 forswitching pixels from being changed by roughness produced during surfacepolishing or stains remaining after cleaning, due to formation of theunderlying insulation film 12 on the entire surface of the TFT arraysubstrate 10.

Furthermore, on the scanning line 3 a, a first interlayer insulationfilm 41 is formed, on which a contact hole 81 communicated with theheavily doped source region 1 d and the contact hole 83 communicatedwith the heavily doped drain region 1 e are formed.

On the first interlayer insulation film 41, the relay layer 71 and thecapacitance line 300 are formed, on which a second interlayer insulationfilm 42 having the contact hole 81 communicated with the heavily dopedsource region 1 d and the contact hole 85 communicated with the relaylayer 71 is formed.

According to the embodiment, ions injected into a polysilicon filmconstituting the semiconductor layer 1 a and the scanning line 3 a maybe activated by baking the first interlayer insulation film 41 at atemperature of about 1000° C. On the other hand, stress produced in thevicinity of the interface of the capacitance line 300 may be relieved bynot doing such baking on the second interlayer insulation film 42.

On the second interlayer insulation film 42, the data line 6 a isformed, and over which a third interlayer insulation film 43, having thecontact hole 85 communicated with the relay layer 71 formed thereon, isformed.

The surface of the third interlayer insulation film 43 is planarized bya CMP (chemical mechanical polishing) treatment so as to reduceorientation defects of the liquid crystal 50 due to steps produced byvarious kinds of wiring and elements existing thereunder. Alternatively,instead of, or in addition to such planarization of the third interlayerinsulation film 43, by forming a groove in at least one of the TFT arraysubstrate 10, the underlying insulation film 12, the first interlayerinsulation film 41, and the second interlayer insulation film 42 so thatwiring of the data line 6 a and the TFT 30, etc. are embedded for theplanarization treatment.

The present invention is not limited to the embodiments described aboveand appropriate modifications can be made within the scope and spirit ofthe invention, which can be understood from the claims and the entirespecification. Electro-optic devices, electronic instruments, andprojection displays followed by such modifications are also includedwithin a technical range of the present invention.

Further, while this invention has been described in conjunction withspecific embodiments thereof, it is evidence that many alternatives,modifications, and variations will be apparent to those skilled in theart. Accordingly, preferred embodiments of the invention as set forthherein are intended to be illustrative, not limiting. Various changesmay be made without departing from the spirit and scope of theinvention.

1. An electro-optic device, comprising: a first substrate; a secondsubstrate; an electro-optic substance sandwiched between the first andsecond substrates; a first zirconia layer located on the opposite sideof the first substrate from the electro-optic substrate; a silica layerlocated on the opposite side of the first zirconia layer from the firstsubstrate; a transparent conductive layer located on the opposite sideof the silica layer from the first zirconia layer, the transparentconductive layer being formed from a transparent conductive material;and a second zirconia layer located on the opposite side of thetransparent conductive layer from the silica layer.
 2. An electro-opticdevice, comprising: a first substrate; a second substrate; anelectro-optic substance sandwiched between the first and secondsubstrates; and an anti-reflection coating located on the opposite sideof the first substrate from the electro-optic substance, theanti-reflection coating including a transparent conductive layersandwiched between two other layers made from anti-static materials. 3.The electro-optic device according to claim 2, wherein an outermostlayer of the anti-reflection coating being zirconia.
 4. Theelectro-optic device according to claim 2, wherein the transparentconductive layer being located between a zirconia layer and a silicalayer.
 5. The electro-optic device according to claim 2, wherein theanti-reflection coating including alternating zirconia and silicalayers.
 6. An electro-optic device, comprising: a first substrate; asecond substrate; an electro-optic substance sandwiched between thefirst and second substrates; a first zirconia layer located on theoutside of the first substrate; a silica layer located on the outside ofthe first zirconia layer; a transparent conductive layer located on theoutside of the silica layer, the transparent conductive layer beingformed from a transparent conductive material; and a second zirconialayer located on the outside of the transparent conductive layer.